The present invention relates to an IMPATT (Impact Avalanche Transit Time) diode composed of a monocrystalline silicon substrate to which a heterostructure-semiconductor layer sequence has been applied in an alternating arrangement of at least two different semiconductor layers forming at least one heterojunction.
IMPATT diodes are powerful millimeter wavelength components. They are utilized, in particular, to generate oscillations.
Avalanche multiplication by impact ionization and movement of the charge carriers through a drift space together may produce a negative resistance. A structure suitable to generate and combine these mechanisms is, for example, a pn-junction.
By using a heterojunction instead of a pn-junction, the voltage required for the avalanche breakdown of the IMPATT diode can be reduced. The heterostructure of the IMPATT diode must be such that the semiconductor material of the generation zone (avalanche breakdown zone) has a smaller band gap than the material of the drift zone. This reduces the ionization threshold energy and thus increases the efficiency of the IMPATT diode.
However, prior art solutions have the drawback that the semiconductor materials employed place the efficiency of the IMPATT diode, for example for a frequency of 80 GHz, at below 10%, and limit the wavelength range to the millimeter range. Moreover, the use of economical Si substrates is possible only within limits.